If you've read my chronic fatigue article, you already know the punchline: my ferritin came back at 28. Technically within the reference range. Technically "normal." And I felt like absolute rubbish.

What I didn't write about in that article was how long it took to get there. Not the blood test itself. That took ten minutes. I mean the months of dragging through work, the weekends where I'd wake up feeling like I hadn't slept, the gym sessions that went from average to genuinely terrible. The slow creep of "maybe this is just what being in my mid-thirties feels like."

It wasn't. It was iron.

And here's the thing that still gets me: iron deficiency is the most common nutritional deficiency in Australia. An estimated 1.1 million Australians are iron deficient, according to published estimates. Among young women aged 18 to 39, research suggests roughly one in three has a ferritin level below 30 µg/L. This isn't obscure. It isn't rare. It's startlingly common, and it's underdiagnosed because the symptoms are so generic that most people (including me) just power through.

My girlfriend, for what it's worth, had an even worse run. Years of heavy periods, progressively worse fatigue, a GP who kept saying "your FBC is fine" without ordering ferritin separately. By the time someone actually checked, her ferritin was 8. She ended up needing an iron infusion. Afterwards, she said it was like someone had turned the lights back on.

That's not a medical claim. It's just what happened to her. But it made me realise how many people are walking around depleted and have no idea, because nobody's looked at the right number.

This article is a full guide to iron studies in Australia. What the tests measure, who should be checking, how to read your results, and what happens if you're low. I've tried to cover the things I wish someone had explained to me before I spent six months blaming my tiredness on everything except the most obvious cause.

A note before we get into it

Iron 101: what it actually does in your body

Iron is an essential mineral that your body cannot produce on its own. Every microgram of iron in your system came from what you ate.

Its most well-known role is in haemoglobin, the protein inside red blood cells that carries oxygen from your lungs to every tissue in your body. About two-thirds of your body's iron sits in haemoglobin. When iron is low, haemoglobin production suffers, oxygen delivery becomes less efficient, and your body has to work harder to maintain the basics. That's why fatigue is the hallmark symptom.

But iron does more than just carry oxygen. It's also involved in energy production at the cellular level (through mitochondrial function), immune system activity, cognitive function, and temperature regulation. So iron deficiency can affect concentration, mood, exercise tolerance, immunity, and even how cold you feel.

Your body stores excess iron primarily as ferritin, a protein that holds iron in reserve until it's needed. Think of ferritin as your iron savings account. Serum iron is what's in your current account. When the savings account runs low, you're in trouble even if the current account looks okay on any given day.

Iron deficiency vs iron deficiency anaemia: the difference matters

This is the distinction that catches a lot of people (and, honestly, sometimes clinicians) off guard.

Iron deficiency means your iron stores are depleted. Your ferritin is low. You may be symptomatic. You may feel exhausted. But your haemoglobin might still be within the reference range on a Full Blood Count, because your body is prioritising haemoglobin production at the expense of other iron-dependent functions. It's a bit like your body borrowing from savings to keep the bills paid. The numbers look okay on the surface, but the reserves are empty.

Iron deficiency anaemia is the later stage. Your stores have been so depleted for so long that your body can no longer maintain adequate haemoglobin levels. Your FBC starts to show it. Haemoglobin drops. Red blood cells may become smaller (microcytic) and paler (hypochromic). This is the stage most people think of when they hear "low iron."

The problem is that most of the focus, in clinical practice and public awareness alike, is on anaemia. If your haemoglobin is fine, you might be told everything's normal. But iron deficiency without anaemia is its own clinical entity, with its own symptoms and consequences. Research increasingly supports that ferritin levels well above the "not anaemic" threshold may be needed to feel well.

This is what happened to me. My FBC was unremarkable. My ferritin was 28. Nobody flagged it until I specifically asked about iron studies. And at 28, I was already noticeably symptomatic.

What iron studies actually measure

When your clinician orders "iron studies," you'll typically get four results back. Here's what each one tells you and how they work together.

How they fit together: No single iron marker tells the full story. The pattern matters:

Low ferritin + low transferrin saturation + high TIBC → likely iron deficiency

Low ferritin + elevated CRP → possible iron deficiency masked by inflammation

Normal ferritin + low transferrin saturation → may indicate functional iron deficiency or chronic disease

Elevated ferritin + normal or high transferrin saturation → possible iron overload (requires further investigation)

Your clinician interprets these as a panel, not individually.

Who's most at risk in Australia

Iron deficiency doesn't affect everyone equally. Several groups carry higher risk.

Menstruating women. Heavy menstrual bleeding is the single most common cause of iron deficiency in premenopausal women in developed countries. Research in Australian women of reproductive age found that 28% reported heavy periods, and these women were far more likely to have had a prior iron deficiency or anaemia diagnosis. If your periods are heavy and your energy is low, that's not a coincidence.

Pregnant women. Iron requirements roughly double during pregnancy. The growing foetus, the expanding blood volume, and the placenta all demand iron. Many women enter pregnancy with already marginal stores, which is why iron deficiency is extremely common during pregnancy and why screening is (or should be) standard antenatal care.

Vegetarians and vegans. Non-haem iron from plant sources is less efficiently absorbed than haem iron from animal products. This doesn't mean plant-based diets inevitably cause deficiency, but they do require more deliberate dietary planning. People on these diets should be tested more regularly. About 14% of women in one Australian screening study followed a vegetarian diet.

Regular blood donors. Each whole blood donation removes approximately 200–250mg of iron. The Australian Red Cross Lifeblood introduced routine ferritin testing for new whole blood donors in 2023 and expanded it to returning donors in 2024, specifically because donor iron depletion was being identified as a real issue.

Endurance athletes. Heavy training increases iron losses through several mechanisms: foot-strike haemolysis, increased gastrointestinal losses, and iron lost in sweat. Athletes, especially female distance runners, are at elevated risk and often undertrained relative to their capacity because of undiagnosed low iron.

People with gastrointestinal conditions. Coeliac disease, Crohn's disease, inflammatory bowel disease, and other conditions affecting the gut can impair iron absorption. Coeliac disease alone is estimated to account for about 3% of iron deficiency anaemia in the general population. Anyone with unexplained iron deficiency that doesn't respond to oral supplementation should be investigated for underlying GI causes.

Older adults. Reduced dietary intake, medications that affect the stomach (proton pump inhibitors, for example), and age-related changes in absorption all contribute.

People who've had bariatric surgery. Bypass procedures can reduce iron absorption surface area in the small intestine.

The "normal ferritin" trap

This is the bit I feel most strongly about. I'm not a clinician, but I've talked to enough people (and lived through this myself) that I think it's worth flagging.

Reference ranges on a lab report are population-based. They represent the statistical range within which most "healthy" people fall. For ferritin, the lower end of many lab reference ranges sits at 15 or even 12 µg/L. A result of 16 gets reported as "normal." No flag. No asterisk. Just a number in the green.

But "not deficient by the narrowest possible definition" is not the same as "optimal." There's growing clinical recognition that many people, especially women, experience symptoms of iron deficiency at ferritin levels well above the lab cutoff. Some GPs and haematologists use a functional threshold of 30 µg/L, and some argue it should be higher for certain populations (athletes, for instance).

My result was 28. "Normal" on the report. But when I actually asked my GP about it, she agreed it was likely contributing to my symptoms and started me on supplementation. Three months later, my ferritin was 65 and I felt noticeably different.

I'm not suggesting everyone with a ferritin of 28 is iron deficient. Context matters. Symptoms matter. But if your ferritin is in the low-normal range and you feel terrible, it's worth having that conversation with your clinician rather than accepting "everything's fine" at face value.

Symptoms that should make you test

Iron deficiency is frustrating because the symptoms are so common and so generic. They overlap with poor sleep, stress, overwork, depression, thyroid issues, vitamin D deficiency, and about a dozen other things.

But when multiple symptoms cluster together, the pattern is worth paying attention to:

Fatigue that doesn't improve with rest. Not "I had a long week" tired. More like "I slept nine hours and still can't function" tired. Persistent, unexplained, disproportionate to your activity level.

Reduced exercise tolerance. Workouts that used to feel moderate now feel brutal. Recovery takes longer. You feel breathless earlier than expected.

Difficulty concentrating. Brain fog, reduced attention span, difficulty with tasks that used to be easy.

Sensitivity to cold. Iron helps regulate body temperature. Feeling cold when others are comfortable, especially cold hands and feet, can be related to iron status.

Pale skin and inner eyelids. In more advanced deficiency, reduced haemoglobin affects skin colour. The inner lining of your lower eyelids, your gums, and your nail beds may appear paler than usual.

Brittle nails and hair changes. Nails that break easily, ridging, or in severe cases, spoon-shaped nails (koilonychia). Increased hair shedding.

Restless legs. An uncomfortable urge to move your legs, particularly at rest or at night. Iron deficiency is one of the most common treatable causes of restless legs syndrome.

Frequent infections. Iron supports immune function, and deficiency has been linked to increased susceptibility to common infections.

None of these individually proves iron deficiency. But if you're experiencing several of them and you haven't had your iron studies checked recently, it's worth ordering the test.

How to prepare for an iron studies test

Getting useful results requires a small amount of prep.

You can find your nearest collection centre here.

Understanding your results

Your iron studies results should be interpreted as a panel, not individual numbers in isolation. But here's a general guide to what the main markers mean at different levels.

Ferritin:

Level	Interpretation
Below 15 µg/L	Depleted iron stores. Consistent with iron deficiency.
15–30 µg/L	Low iron stores. Many clinicians consider this functionally low, particularly if symptoms are present.
30–100 µg/L	Generally adequate for most people.
Above 200 µg/L (women) or 300 µg/L (men)	May indicate iron overload, inflammation, or liver conditions. Worth discussing with your GP.

Transferrin Saturation:

Level	Interpretation
Below 16%	Suggests inadequate iron supply to tissues.
16–45%	Generally adequate.
Above 45%	May indicate iron overload. Warrants further investigation.

TIBC:

Level	Interpretation
Elevated	Typically seen with iron deficiency (body is trying to capture more iron).
Low	May be seen with iron overload, chronic disease, or liver conditions.

A few important caveats. These are general guidelines, not diagnostic thresholds. Different labs may use slightly different reference intervals. Pregnancy, inflammation, liver disease, chronic conditions, and medications can all shift these numbers. Interpretation always depends on the full clinical context.

What happens after a low result

If your iron studies confirm deficiency, the next steps depend on the severity and the likely cause.

Oral iron supplementation is the standard first-line treatment for mild to moderate deficiency. Your GP will recommend a dose and formulation based on your result and symptoms. Oral iron is cheap, accessible, and effective. But it's not always well-tolerated. Constipation, nausea, and stomach upset are common side effects, and adherence can be a challenge.

Some practical tips that may help: taking iron with vitamin C (like a small glass of orange juice) may improve absorption. Taking it every other day rather than daily may actually improve absorption efficiency, based on more recent research. Avoiding tea, coffee, dairy, and calcium supplements within an hour or two of your iron dose can reduce interference with absorption.

Iron infusions (intravenous iron) are used for more severe deficiency, when oral iron isn't tolerated or isn't working, or when there's an urgent need to replenish stores quickly. Before surgery or in late pregnancy, for example. My girlfriend's infusion was straightforward: a few hours at a clinic, and she noticed improvement within a couple of weeks.

Investigating the cause is just as important as treating the deficiency. Iron deficiency doesn't happen in a vacuum. Your clinician should be thinking about why your iron is low. Heavy periods, dietary insufficiency, GI bleeding, malabsorption, chronic disease. If the cause isn't addressed, supplementation is just topping up a leaking tank.

For unexplained iron deficiency, especially in men and in postmenopausal women where menstrual loss isn't a factor, investigation for gastrointestinal causes (including coeliac disease and occult bleeding) is important.

Tests to consider through Bloody Good

The iron test:

Iron Studies Blood Test (Including Ferritin). The full panel: serum iron, ferritin, transferrin saturation, and TIBC. This is the test you want, not just a standalone ferritin.

Related tests that give a more complete picture:

Full Blood Count (FBC). Haemoglobin, red blood cell indices (including MCV, which tells you about red blood cell size). Essential for determining whether iron deficiency has progressed to anaemia.

High-Sensitivity CRP. Useful if you suspect inflammation might be masking your ferritin result.

Vitamin B12. B12 deficiency can cause anaemia and overlapping symptoms. Worth testing alongside iron, especially if your diet is restricted.

Folate. Works with B12 and iron for red blood cell production.

Vitamin D (25-OH). Commonly low alongside iron in people with fatigue, and worth checking in the same blood draw.

If you'd rather cover everything at once:

The Bloody Good Test covers 100 biomarkers including iron studies, FBC, vitamin D, B12, liver function, thyroid, cholesterol, and more. If you're going to sit in the pathology chair anyway, getting the full picture in one go makes sense.

Biomarker info: Ferritin

When to retest

After starting supplementation: Retest ferritin after 3 months of consistent supplementation. This gives enough time for stores to shift meaningfully. Don't test after 2 weeks and panic because nothing's changed. It takes time.

After an infusion: Your clinician will typically retest 4–8 weeks after an iron infusion to assess the response.

If you're in a high-risk group: Women with heavy periods, athletes in hard training, regular blood donors, and people with GI conditions should consider testing iron studies at least annually. More often if they've had a previous deficiency.

If symptoms return: If you felt better on supplementation and then your energy drops again after stopping, your stores may have depleted again. Retest and reassess.

If you're planning pregnancy: Check iron studies before conception if possible. Starting pregnancy with adequate stores is far easier than trying to catch up once demand doubles.

A general principle: iron studies are most useful when you can compare over time. Save your results. Track the trend. A single ferritin number is a snapshot. Two or three results across 6–12 months tell you whether you're maintaining, building, or losing stores — and that trajectory matters more than any single data point.

Explore more biomarkers

If you want to go deeper into any of the markers mentioned here, or explore related tests for fatigue, anaemia, or nutritional health, the Bloody Good biomarker directory has detailed pages on what each test measures and how to think about results in general terms.

Browse the Bloody Good Biomarker Directory